This is a great thread! Some additional data points:
BLL - Zleep Hotel is within the airport grounds and is less than 5 minutes walk from the terminal. It feels like a Travelodge and is full of families visiting nearby Legoland.
CDG - Ibis is within walking distance (as already in the Wiki)
BSL - Ibis Basel has a free airport shuttle; it's a 10-15 minute drive and you have to call them to pick you up on arrival
HAJ - Maritim Airport Hotel is literally next to the terminal - less than 5 minutes walk